M40 sniper rifle was formally adopted by US Marine Corps in 1966 and widely used through the Vietnam War and subsequent conflicts. In its original version it was a “militarized” version of a highly successful Remington model 700 sporting rifle with short action, optimized for cartridges not significantly longer than .308 Win / 7.62mm NATO. It featured traditional wooden stock, integrated non-removable magazine and Redfield 3-9X telescope sight. Actual M40 rifles were built by USMC ordnance people from components supplied by Remington and other contractors at their base in Quantico.

During 1970s M40 rifles were upgraded to M40A1 configuration, which featured new McMillan stocks made from polymer and new Unertl 10X telescope sights.

The M40A3 was the next step in evolution of the M40 sniper rifle system, and it was adopted in around 2001. M40A3 feature same Remington model 700 “short” actions but with different barrels and improved McMillan stocks.

Since 2009, the M40A3 configuration was superseded by yet another version, known as M40A5. M40A5 rifles are either build “from the scratch” or upgraded from earlier M40A3 with installation of a new polymer stock with detachable magazine feed system developed by Badger Ordnance, and Schmidt & Bender telescope sights.

The latest iteration of venerable M40 sniper rifle system is the M40A6 (development name) / M40A7 (actual name), which is scheduled to enter service with USMC in around 2017. This is yet another incremental upgrade to the basic weapon, which introduces a Remington-designed modular chassis with folding shoulder stock and more Picatinny rails.

All M40 sniper rifles are based on the Remington Model 700 bolt action rifles with short actions. All models up to M40A3 feature integral, non-detachable box magazines with 5-round capacity, which are loaded through the top of the action, with bolt retracted. Since M40A5 these rifles are equipped with 10-round detachable magazines. M40 rifles have wooden stocks, M40A1, M40A3 and M40A5 feature McMillan polymer stocks of various designs, and M40A7 features Remington modular folding stock. In all versions M40 rifles have no iron sights, and issued either with daytime telescope sights or with various night / IR sights, according to the mission plan. Up to M40A3 barrels are provided with match crown at the muzzle; since M40A5, barrels feature threaded muzzles to accept sound suppressors (silencers).